Sensory properties of teeth and periodontium are not well understood, both because of difficulties in dividing single-unit studies of dental tissue, and bacause of insufficient information of the distribution of trigeminal gasserian and mesencephalic nerve endings, the utlrastructure of these endings, and their relationship to autonomic nerves and to odontoblasts or periodontal cells. Recently, by using autoradiography to detect nerves labeled by radioactive axonal transport, we have demonstrated gasserian nerve endings in rats, and have described the ultrastructure of the dentinal and pulpal endings. The proposed research will use similar methods to study dental innervation in monkeys and rats. The specific objectives are: (1) to map mesencephalic and autonomic nerve endings in rat and monkey teeth and periodontium: (2) to develop a procedure for labeling gasserian endings in monkeys and to map these endings in monkey molars, canines, incisors, and periodontium; (3) to compare the ultrastructure of labeled gasserian and mesencephalic endings using EM-autoradiography; (4) to determine the kinds of junctions formed by trigeminal or autonomic nerve endings and odontoblasts or periodontal cells; (5) to measure the sizes of axons derived from labelled gasserian, mesencephalic, or autonomic nerve endings; (6) to study innervation in extracted monkey teeth. This research will contribute to our understanding of the cellular basis of dental pain and proprioception; to determination of the role of autonomic innervation in dental sensitivity; and to identification of the kinds of innervation that typify all mammalian teeth as opposed to innervation unique to particular species or types of teeth. The long-range goal is to correlate these studies with functional studies to provide greater insight into the mechanisms of dental sensitivity and pain.